Mesoporous polyacrylonitrile and carbon fibers have been prepared by electrospinning and subsequent supercritical drying and carbonization. Polyvinylpyrrolidone was used as a template. Ambient drying, oxidation, and supercritical drying were conducted to investigate the effects of treatment methods on the structure of the fibers. Interesting surface morphologies of the fibers, including nanoconvexities and nanorods, were found when the different drying methods were used. The surface area of the mesoporous carbon fibers was estimated as 602.0 m2 g-1, with an average pore size of 3.6 nm.